From the logs everything seems to be working fine. Why do you think it's not working?

It fetches all refs/heads, which includes refs/heads/v2spa. Then it can just checkout v2spa, which is a local branch tracking refs/heads/v2spa:

Fetching +refs/heads/*:refs/heads/*
running "git fetch -v --progress origin +refs/heads/*:refs/heads/*" in "/b/build/slave/cache_dir/chromium.googlesource.com-catapult"
From https://chromium.googlesource.com/catapult
 = [up to date]          gh-pages               -> gh-pages
 = [up to date]          infra/config           -> infra/config
 = [up to date]          master                 -> master
 = [up to date]          md-pages               -> md-pages
 = [up to date]          v2spa                  -> v2spa
 = [up to date]          vulcanized_traceviewer -> vulcanized_traceviewer
fetch +refs/heads/*:refs/heads/* took 0.0 minutes

Also, once it checks it out, it applies the patch on top of https://chromium.googlesource.com/catapult/+/d63d9afeb8a5225b4c6db3aad513ddb7b685a97e

0:00:00] ===Applying patch ref===
[0:00:00] Repo is 'https://chromium.googlesource.com/catapult' @ 'refs/changes/06/1123406/1', ref is 'd63d9afeb8a5225b4c6db3aad513ddb7b685a97e', root is '/b/build/slave/Catapult_Presubmit/build/catapult'
[0:00:00] Finished.

The git cache has indeed refs/heads/v2spa as local ref. But builder's git checkout treats cache as a remote "origin", hence it should checkout origin/v2spa.


Relevant quote from log:



===Running git fetch origin ===
In directory: /b/build/slave/Catapult_Presubmit/build/catapult
===Succeeded in 0.0 mins of git fetch origin ===

===Running git checkout --force v2spa -- ===
In directory: /b/build/slave/Catapult_Presubmit/build/catapult
Warning: you are leaving 1 commit behind, not connected to
any of your branches:

  702a1dfb8 Committed patch

If you want to keep it by creating a new branch, this may be a good time
to do so with:

 git branch <new-branch-name> 702a1dfb8

Switched to branch 'v2spa'
Your branch is behind 'origin/v2spa' by 4 commits, and can be fast-forwarded.
  (use "git pull" to update your local branch)
===Succeeded in 0.0 mins of git checkout --force v2spa -- ===

Issue 860430 has been merged into this issue.

Bumping priority because v8 got hit by this too, so it's clearly a regression.

So, I went to old V8 build [1] and I can see in its log [2] the correct invocation:
  ===Running git checkout --force origin/vee-eight-lkgr -- ===
  
[1] https://ci.chromium.org/p/v8/builders/luci.v8.ci/V8%20Linux64%20-%20node.js%20baseline/2000
[2] https://logs.chromium.org/v/?s=v8%2Fbuildbucket%2Fcr-buildbucket.appspot.com%2F8945527683566252960%2F%2B%2Fsteps%2Fbot_update%2F0%2Fstdout

And in most recent build https://ci.chromium.org/p/v8/builders/luci.v8.ci/V8%20Linux64%20-%20node.js%20baseline/4011
  ===Running git checkout --force vee-eight-lkgr -- ===

So regression happened sometime between May 25th and July 4th. Bisecting by hand:

3529 -> good https://ci.chromium.org/p/v8/builders/luci.v8.ci/V8%20Linux64%20-%20node.js%20baseline/3529

3530 -> bad https://ci.chromium.org/p/v8/builders/luci.v8.ci/V8%20Linux64%20-%20node.js%20baseline/3530

which provides range of 2018-06-26 11:07 AM (PDT) .. 2018-06-26 11:37 AM (PDT)
but recipe bundler might be slightly behind, so allow bigger window to the passed, which approximately matches https://chromium-review.googlesource.com/c/chromium/tools/build/+/1114217

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/tools/depot_tools/+/4fb2477d0870024db541206ca02885c3e0ac4990

commit 4fb2477d0870024db541206ca02885c3e0ac4990
Author: Edward Lemur <ehmaldonado@chromium.org>
Date: Fri Jul 06 22:33:37 2018

bot_update: Fix syncing to branches.

When syncing remote branches, checkout origin/<branch> instead of
<branch>, since there might be a local branch with that name.

Bug:  859703 
Change-Id: I9a49b940f53f75a97e5458fdcf578c3b52b26de2
Reviewed-on: https://chromium-review.googlesource.com/1128271
Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>

[modify] https://crrev.com/4fb2477d0870024db541206ca02885c3e0ac4990/recipes/recipe_modules/bot_update/resources/bot_update.py

Seems to be working now, thank you!
https://build.chromium.org/p/tryserver.client.catapult/builders/Catapult%20Presubmit/builds/12504/steps/bot_update/logs/stdio

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f25fc05367e547656d7cf57eeba53530991190ab

commit f25fc05367e547656d7cf57eeba53530991190ab
Author: depot-tools-chromium-autoroll <depot-tools-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Date: Fri Jul 06 23:43:15 2018

Roll src/third_party/depot_tools 3c023259d75c..4fb2477d0870 (1 commits)

https://chromium.googlesource.com/chromium/tools/depot_tools.git/+log/3c023259d75c..4fb2477d0870


git log 3c023259d75c..4fb2477d0870 --date=short --no-merges --format='%ad %ae %s'
2018-07-06 ehmaldonado@chromium.org bot_update: Fix syncing to branches.


Created with:
  gclient setdep -r src/third_party/depot_tools@4fb2477d0870

The AutoRoll server is located here: https://depot-tools-chromium-roll.skia.org

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

If the roll is causing failures, please contact the current sheriff, who should
be CC'd on the roll, and stop the roller if necessary.



BUG= chromium:859703 
TBR=agable@chromium.org

Change-Id: Ia1e9101dd98d9fb49b443e6d61e0a33c889d04b0
Reviewed-on: https://chromium-review.googlesource.com/1128366
Reviewed-by: depot-tools-chromium-autoroll <depot-tools-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Commit-Queue: depot-tools-chromium-autoroll <depot-tools-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#573119}
[modify] https://crrev.com/f25fc05367e547656d7cf57eeba53530991190ab/DEPS

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/tools/depot_tools/+/92745a5b0e2e7593fabe8b831cb913cd548b257b

commit 92745a5b0e2e7593fabe8b831cb913cd548b257b
Author: Edward Lemur <ehmaldonado@chromium.org>
Date: Fri Jul 06 23:50:17 2018

bot_update: Fix syncing to origin/*.

Skip adding origin if the branch name already has 'origin/'.

Bug:  859703 
Change-Id: I0141c04189d00187c202a7885a7c6bb74571e7ea
Reviewed-on: https://chromium-review.googlesource.com/1128390
Reviewed-by: Vadim Shtayura <vadimsh@chromium.org>
Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Commit-Queue: Andrii Shyshkalov <tandrii@chromium.org>

[modify] https://crrev.com/92745a5b0e2e7593fabe8b831cb913cd548b257b/recipes/recipe_modules/bot_update/resources/bot_update.py

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/9083b8187ea0f7d9d7f6046773dcace5e1d0e40c

commit 9083b8187ea0f7d9d7f6046773dcace5e1d0e40c
Author: depot-tools-chromium-autoroll <depot-tools-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Date: Sat Jul 07 01:30:12 2018

Roll src/third_party/depot_tools 4fb2477d0870..92745a5b0e2e (1 commits)

https://chromium.googlesource.com/chromium/tools/depot_tools.git/+log/4fb2477d0870..92745a5b0e2e


git log 4fb2477d0870..92745a5b0e2e --date=short --no-merges --format='%ad %ae %s'
2018-07-06 ehmaldonado@chromium.org bot_update: Fix syncing to origin/*.


Created with:
  gclient setdep -r src/third_party/depot_tools@92745a5b0e2e

The AutoRoll server is located here: https://depot-tools-chromium-roll.skia.org

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

If the roll is causing failures, please contact the current sheriff, who should
be CC'd on the roll, and stop the roller if necessary.



BUG= chromium:859703 
TBR=agable@chromium.org

Change-Id: Ia39b89af2f2530668da8fb8125f2e08a50a89ab0
Reviewed-on: https://chromium-review.googlesource.com/1128395
Reviewed-by: depot-tools-chromium-autoroll <depot-tools-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Commit-Queue: depot-tools-chromium-autoroll <depot-tools-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#573137}
[modify] https://crrev.com/9083b8187ea0f7d9d7f6046773dcace5e1d0e40c/DEPS

Thanks a bunch Andrii for the analysis! And thanks Edward for the fix! Seems to be fixed for V8 too now.